Geographically there has always been some debate as to where the Northeastern United States begins and ends. The vast area from northern Virginia (outside Washington DC) to northern Maine, and from western Pennsylvania (Pittsburgh) to the Atlantic Ocean, have all been loosely grouped into the Northeast at one time or another. Much of the debate has been what the cultural, economic, and urban aspects of the Northeast are, and where they begin or end as one reaches the borders of the region.

Using the Census Bureaus definition of the northeast, the region includes nine states: they are Maine, New York, New Jersey, Vermont, Massachusetts, Rhode Island, Connecticut, New Hampshire, and Pennsylvania.[1][a] The region is often subdivided into New England (the six states east of New York) and the Mid-Atlantic states (New York, New Jersey, and Pennsylvania). This definition has been essentially unchanged since 1880 and is widely used as a standard for data tabulation.[7][8][9][10] However, the Census Bureau has acknowledged the obvious limitations of this definition[11] and the potential merits of a proposal created after the 1950 census that would include changing regional boundaries to include Delaware, Maryland, and Washington, D.C. with the Mid-Atlantic states, but ultimately decided that "the new system did not win enough overall acceptance among data users to warrant adoption as an official new set of general-purpose State groupings. The previous development of many series of statistics, arranged and issued over long periods of time on the basis of the existing State groupings, favored the retention of the summary units of the current regions and divisions."[12] The Census Bureau confirmed in 1994 that it would continue to "review the components of the regions and divisions to ensure that they continue to represent the most useful combinations of States and State equivalents."[12]

Many organizations and reference works follow the Census Bureau's definition for the region;[13][14][15] however, other entities define the Northeastern United States in significantly different ways for various purposes. The Association of American Geographers divides the Northeast into two divisions- "New England", which consists of Maine, Vermont, New Hampshire, Massachusetts, Rhode Island and Connecticut, and the "Middle States", which consists of New York, Pennsylvania, New Jersey, and Delaware.[16] Similarly, the Geological Society of America defines the Northeast as these same states but with the addition of Maryland and the District of Columbia.[17] The narrowest definitions include only the states of New England.[18] Other more restrictive definitions include New England and New York as part of the Northeast United States, but exclude Pennsylvania and New Jersey.[19][20] States beyond the Census Bureau definition that other entities include in the Northeast United States are:

Anthropologists recognize the "Northeastern Woodlands" as one of the cultural regions that existed in the Western Hemisphere at the time of European colonists in the 15th and later centuries. Most did not settle in North America until the 17th century. The cultural area, known as the "Northeastern Woodlands", in addition to covering the entire Northeast U.S., also covered much of what is now Canada and others regions of what is now the eastern United States.[32] Among the many tribes that inhabited this area were those that made up the Iroquois nations and the numerous Algonquian peoples.[33] In the United States of the 21st century, 18 federally recognized tribes reside in the Northeast.[34] For the most part, the people of the Northeastern Woodlands, on whose lands European fishermen began camping to dry their codfish in the early 1600s, lived in villages, especially after being influenced by the agricultural traditions of the Ohio and Mississippi valley societies.[35]

All of the states making up the Northeastern region were among the original Thirteen Colonies, though Maine, Vermont, and Delaware were part of other colonies before the United States became independent in the American Revolution. The two cultural and geographic regions that form parts of the Northeastern region have distinct histories.

Although the first settlers of New England were motivated by religion, in more recent history, New England has become one of the least religious parts of the United States. In a 2009 Gallup survey, less than half of residents in Vermont, New Hampshire, Maine, and Massachusetts reported religion as an important part of their daily life.[40] In a 2010 Gallup survey, less than 30% of residents in Vermont, New Hampshire, Maine, and Massachusetts reported attending church weekly, giving them the lowest church attendance among U.S. states.[41]

The first European explorer known to have explored the Atlantic shoreline of the Northeast since the Norse was Giovanni da Verrazzano in 1524. His ship La Dauphine explored the coast from what is now known as Florida to New Brunswick. Henry Hudson explored the area of present-day New York in 1609 and claimed it for the Netherlands. His journey stimulated Dutch interest, and the area became known as New Netherland. In 1625, the city of New Amsterdam (the location of present-day New York City) was designated the capital of the province.[44] The Dutch New Netherland settlement along the Hudson River and, for a time, the New Sweden settlement along the Delaware River divided the English settlements in the north and the south. In 1664, Charles II of England formally annexed New Netherland and incorporated it into the English colonial empire.[45] The territory became the colonies of New York and New Jersey.[45] New Jersey was originally split into East Jersey and West Jersey until the two were united as a royal colony in 1702.[45]

Penn strongly desired access to the sea for his Pennsylvania Province and leased what then came to be known as the "Lower Counties on the Delaware"[47] from the Duke.

Penn established representative government and briefly combined his two possessions under one General Assembly in 1682. However, by 1704 the Province of Pennsylvania had grown so large that their representatives wanted to make decisions without the assent of the Lower Counties and the two groups of representatives began meeting on their own, one at Philadelphia, and the other at New Castle. Penn and his heirs remained proprietors of both and always appointed the same person Governor for their Province of Pennsylvania and their territory of the Lower Counties. The fact that Delaware and Pennsylvania shared the same governor was not unique. From 1703 to 1738, New York and New Jersey shared a governor.[48] Massachusetts and New Hampshire also shared a governor for some time.[49]

As of 2007[update], forest-use covered approximately 60% of the Northeastern states (including Delaware, Maryland, and the District of Columbia), about twice the national average. About 12% was cropland and another 4% grassland pasture or range. There is also more urbanized land in the Northeast (11%) than any other region in the U.S.[25]

The climate of the Northeastern United States varies from northernmost Maine to southernmost Maryland. The climate of the region is created by the position of the general west to east flow of weather in the middle latitudes that much of the USA is controlled by and the position and movement of the subtropical highs. Summers are normally warm in northern areas to hot in southern areas. In summer, the building Bermuda High pumps warm and sultry air toward the Northeast, and frequent (but brief) thundershowers are common on hot summer days. In winter the subtropical high retreats southeastward, and the polar jet stream moves south bringing colder air masses from up in Canada and more frequent storm systems to the region. Winter often brings both rain and snow as well as surges of both warm and cold air. [51]

The basic climate of the Northeast can be divided into a colder and snowier interior (Pennsylvania and New York State, and New England), and a milder coast and coastal plain from southern Rhode Island southward, including, New Haven, CT, New York City, Philadelphia, Trenton, Wilmington, Baltimore...etc.). Annual mean temperatures range from the low 50s F from Maryland to southern Connecticut, to the 40s F in most of New York State, New England, and northern Pennsylvania.[51][52][53]

New York City, the most populous city in the Northeast and all of the United States

Philadelphia, the second most populous city in the Northeast and the fifth most populated city in the United States

Boston, the most populated city in Massachusetts and New England and the third most populated city in the Northeast

Pittsburgh, the second most populous city in Pennsylvania, and the fourth most populous city in the Northeast

As of the July 2013 U.S. Census Bureau estimate, the population of the region totaled 55,943,073.[54] With an average of 345.5 people per square mile, the Northeast is 2.5 times as densely populated as the second-most dense region, the South. Since the last century, the U.S. population has been shifting away from the Northeast (and Midwest) toward the South and West.[55]

The two U.S. Census Bureau divisions in the Northeast (New England and Mid-Atlantic) rank #1 and #2 among the 9 divisions in population density according to the 2013 population estimate. The South Atlantic region (233.1) was very close behind New England (233.2). Due to the faster growth of the South Atlantic region, it will take over the #2 division rank in population density in the next estimate, dropping New England to 3rd position. New England is projected to retain the number 3 rank for many, many years, as the only other lower-ranked division with even half the population density of New England is the East North Central division (192.1) and this region's population is projected to grow slowly. [b][56]

Geographer Wilbur Zelinsky asserts that the Northeast region lacks a unified cultural identity,[3] but has served as a "culture hearth" for the rest of the nation.[62] Several much smaller geographical regions within the Northeast do have distinct cultural identities.[3]

According to a 2009 Gallup poll, the Northeastern states differ from most of the rest of the U.S. in religious affiliation, generally reflecting the descendants of immigration patterns of the late 19th and early 20th centuries, with many Catholics arriving from Ireland, Italy, Canada, and eastern Europe. Massachusetts, Rhode Island, New York, and New Jersey are the only states in the nation where Catholics outnumber Protestants and other Christian denominations. More than 20% of respondents in Maine, New Hampshire, and Vermont declared no religious identity.[64] Compared to other U.S. regions, the Northeast, along with the Pacific Northwest, has the lowest regular religious service attendance and the fewest number of people for whom religion is an important part of their daily lives.[65]

The Northeastern United States tended to vote Republican in federal elections through the first half of the 20th century, but the region has since the 1990s shifted to become the most Democratic in the nation.[23] Results from a 2008 Gallup poll indicated that eight of the top ten Democratic states were located in the region, with every Northeastern state having a Democratic party affiliation advantage of at least ten points.[70] The following table demonstrates Democratic support in the Northeast as compared to the remainder of the nation.[71]

The following table shows the breakdown of party affiliation of governors, state legislative houses, and U.S. congressional delegation for the Northeastern states, as of 2017[update]. (Demographics reflect registration-by-party figures from that state's registered voter statistics.)

^The U.S. Census Bureau reorganized its administrative units, and its regional offices do not cover the Census regions (the northeastern most regional office headquartered in New York City covers New England, New York, New Jersey, and Puerto Rico).[6]

^Based on U.S. Census Bureau population projections to 2030 (and assuming constant land area) the population density for the South Atlantic division will increase significantly to 294.6/mi2, New England's density will increase to 249.2/mi2 and the East North Central division will increase only slightly to 200.2/mi2. The division with the 5th highest density is projected to be the East South Central division at 111.6/mi2.[56]

^Zelinsky, Wilbur (December 1955). "Some Problems in the Distribution of Generic Terms in the Place-Names of the Northeastern United States". Annals of the Association of American Geographers. 45 (4). doi:10.1111/j.1467-8306.1955.tb01491.x.